Drew, welcome. Yes, an M3 would work as a vertical center with M22s, but unless you have some specific reason for preferring the M3, the M2 might be a better choice. The M2 is an almost exact match in timbre for the M22s above about 90Hz, while the M3 uses a different driver with a slightly different(although very good)sound.

I ran three M3s across the front with real good luck for a couple of years. Since then, I have been using an M3 as center with M50s as mains and they work just great! Of course they all use the same complement of tweets and mid-woofs, so they sound neigh near identical! Rich.

Would there be a noticable sonic difference from using an M3 centre with M22 mains do you think? I myself am thinking of getting 2 M3s (one above the screen, one below) and if it doesn't work out, I can always use them upstairs.